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Parity Checker and Generator

When digital data is transmitted from one location to another, it is necessary to know at the receiving end whether the received data is free of error. A simple form of error detection is achieved by adding an extra bit to the transmitted word. This additional bit is known as the parity bit and it decides whether the data transmitted is errorfree or not. There are two types of parity bits, namely even parity and odd parity. In an even parity system, the parity bit added to the word to be transmitted is chosen so that the number of 1’s in the modified word is even. For example, 101011 has even parity because it contains four 1’s. The ASCII code for the decimal digit 9 is 0111001. This would require the addition of a 0 in the most significant place to give even parity in the modified word, which is now written as (9)10= 0 0111001. 0 – Parity bit. Odd parity means an n-bit input has an odd number of 1’s. The ASCII code for the decimal digit 9 (0111001) would require the addition of a 1 in the most significant place to give odd parity in the modified word, which is now written as (9)10 = 1 0111001 .1 – Parity bit. The example given in table which uses an8 4 2 1 code, shows a parity bit which makes the number of the 1’s in each code group as odd.